Closed all browsers, started a new Firefox profile and logged in, no change.
I had two 14TB parity drives (you can still see them attached in the Unassigned Devices section); I just switched over to 16TB parity drives, one of them finished building and is assigned as parity, the other was building when the power outage happened.
I haven't yet figured out a way to automate the shutdown of my unRAID when it's on UPS, but I appreciate the advice.